1. Field of Endeavor
The present disclosure relates to a relay dualization apparatus, and more particularly to a relay dualization apparatus used for substation automation system.
2. Background
This section provides background information related to the present disclosure which is not necessarily prior art.
Communications among relays in substation systems have been developed and will progress toward more economical and efficient ways.
A communication standard for communication between the secondary devices of a substation has been introduced by the International Electrotechnical Committee (IEC) as part of the standard IEC 61850 entitled “communication networks and systems in substations”. In Korea, Jeju substation has been using the IEC 61850 protocol since 2005, followed by Sanchong substation in 2007.
Ethernet is used as a basic communication medium of IEC 61850 protocol. However, the standardized method of using Ethernet excludes a regulation on dualization that is required in the existing power system. The conventional power system forms a communication port in dualization for stability, or operates main/preliminary systems by installing same equipment in duplication.
The method of forming the communication port in duplication is disadvantageous in that, although economically advantageous, it takes many hours to restore an entire system, in a case there is generated an error in the system. Furthermore, the method of installing equipment in duplication may be advantageous due to its stability but is disadvantageous in that the installation cost is doubled in the course of system formation. Now, a conventional substation system will be described with reference to drawings.
FIG. 1 is a structural view of a substation system connected in hard-wired method according to prior art.
Relays (140 to 143) in the conventional substation system is connected to switch gears (150 and 152) as lower units and CT (Current Transformer)/PTs (Power Transformers, 151 and 153) using a wire, and process by receiving data information at a contact point.
Furthermore, the relays (140 to 143) relay data received from the lower units (150˜153) via a predetermined protocol (e.g., Modbus or DNP, etc.) to a higher system including an interlocking unit (110), a RTU (Remote Terminal Unit, 120) and HMI (Human Machine Interface, 130) using RS-232/485 communication line.
The conventional system thus described in FIG. 1 uses a dualization method for dualization in which a preliminary device (relay B, 141) relative to a main device (relay A, 140) is formed in duplication, and the preliminary device (relay B, 141) is operated when an error is generated on the main device (relay A, 140). In other words, devices are installed in duplication to disadvantageously increase the installation cost.
FIG. 2 is a structural view illustrating a substation system using IEC 61850 protocol.
Referring to FIG. 2, the substation system using the IEC 61850 protocol is such that relays (250 to 253) receive data from lower units of switch gears (270 and 272) or CT/PTs (271 and 273) via Ethernet switches (260 and 261). The relays (250 to 253) transmit the data to a control center (200) and HMIs (220 and 221) via an Ethernet switch (230).
Although DNP or Modbus was used in the system illustrated in FIG. 1, the IEC 61850 is being used as a communication protocol in response to evolution to a digital substation system illustrated in FIG. 2. However, even in FIG. 2, the relays B (251 and 253) are used as preliminary devices of relays A (250 and 252) which are main bodies to disadvantageously increase an installation cost.
FIGS. 3a and 3b are exemplary views for illustrating a network method in a conventional substation system, where a substation system is shown that is configured with a network of each relay and HMIs (300 and 301) by way of a ring network and a star network.
As noted from the foregoing, the conventional digital substation system is disadvantageous in that relays are overlapping installed to increase the installation cost, such that a communication port is dually installed to form a ring network (FIG. 3a) or a star network (FIG. 3b).
In a ring network of FIG. 3a, the relay 1 (321) communicates with the HMI (300) via a switch (310) using a communication line connected to an upper side thereof (clockwise). Likewise, relays 2 and 3 (322, 323) communicate to the same direction. If there is generated an error in the communication line between the relays 1 (321) and the switch (310), the relay 1 (321) communicates with the HMI (300) via the switch (310) using a communication line connected to a bottom side thereof (counterclockwise). At this time, the relay 2 (322) and the relay 3 (323) also communicate counterclockwise.
In a star network of FIG. 3b, a relay 1 (324) communicates with the HMI (301) via a switch (311), but communicates with the HMI (301) via a switch (312), if there is generated an error on the communication line between the two. Relay 2 (325) and relay 3 (326) also communicate with the HMI (301) using a normal state of communication line among the switch 1 (311) and the switch 2 (312) on the same condition.
That is, in the conventional substation system using the above networks, in a case there is generated an error on the communication line, communication is carried out using an opposite direction of communication line (FIG. 3a) or a switch is replaced (FIG. 3b). This may be an economical method as a dualization scheme to network errors, but due to the fact that a relay is an important device conducting monitoring and control in a complex power system, such that frequent losses may be generated due to unstable system state and overload. Thus, a defective state continues for an entire system until an apparatus generated with an error is returned to a normal state, if a relay is generated with an error in the conventional system, disadvantageously causing a fatal influence to the system.